In recent years, there is proposed a wiring substrate for mounting a light emitting device thereon. For example, the wiring substrate may include a wiring part having a wiring that is patterned on a substrate and an insulating layer that selectively exposes the wiring. In the wiring substrate, the wiring that is exposed from the insulating layer is used as a terminal that is electrically connected to a semiconductor device (see, for example, Japanese Laid-Open Patent Publication No. 2013-65621).
Because the semiconductor device such as alight emitting device generates heat during operation, the temperature of the semiconductor device may need to be prevented from surpassing a predetermined temperature. Therefore, in some cases, the wiring substrate may have a heat radiation plate provided on the wiring part interposed by an adhesive layer. However, because the adhesive layer is adhered only to a lower surface of the substrate of the wiring part (the surface on the side of the heat radiation plate), the adhesive layer may be heated to a high temperature due to the heat generated by the semiconductor device. Further, adhesive strength between the heat radiation plate and the wiring part may be degraded in a case where the semiconductor device is repeatedly stored in a low temperature environment when the semiconductor device is not operating.